The invention relates to a device for the relative angular adjustment of an internal combustion engine camshaft in relation to its crankshaft wherein an adjusting bushing is rotationally fixed on the input end of the camshaft and has external gear teeth. An input sleeve with internal gear teeth surrounds the adjusting bushing and is connected to an input gear. An actuator is displaceably arranged between the input sleeve and adjusting bushing and has double gear teeth, one in engagement with the internal gear teeth of the input sleeve and the other in engagement with the external gear teeth of the adjusting bushing and wherein at least one gear teeth pair is designed with helical teeth. A spring holds the actuator in an initial position and rotational movement of the camshaft is limited by a stop.
A device of this general construction is known from DE-OS 3,316,162. In this device, an actuation path of the actuator arranged between input sleeve and adjusting bushing is limited by stops. Here, the stops are effective between the actuator and adjoining components of the device. Due to this arrangement of the stops, stressing of the gear teeth between input sleeve and adjusting bush is not possible. This has the disadvantage that in the end positions of the actuator, rattling noises can occur in the gear teeth due to backlash arising from production tolerances.
An object on which the invention is based is to create a device for relative angular adjustment of a camshaft and crankshaft in which stressing is achieved in the gear teeth between an input sleeve and adjusting bushing in at least an end position of the actuator.
This object is achieved by virtue of having the stop mechanism act between the input sleeve and the adjusting bushing.
By shifting of the stop away from the actuator, the actuator can move in the gear teeth in a stop-free fashion in at least one adjustment direction. Limiting the adjusting movement in one end position is achieved by having the stop act between the input sleeve and camshaft. As a result, the actuator is pressed into the gear teeth of the input sleeve and camshaft, which are blocked with respect to one another by the stop when the actuator is moved into an end position under the pressure of a spring or some other control means, e.g. under the pressure of the lubricating oil from the lubricating oil circuit.
The backlash is bridged by virtue of the resulting stressing in the gear teeth and the occurrence of rattling noises is avoided in an advantageous manner.
It has been found that the rattling noises are strongest in the starting and idling phase of the internal combustion engine. In these operating phases, the adjusting device is in a so-called initial position, (i.e. the angular adjustment between input sleeve and camshaft is equal to zero and the camshaft is set to "retard") and the actuator is in an end position. To eliminate rattling noises in this initial position of the device, it is sufficient if the stop is effective between the input sleeve and camshaft. The actuator is stop-free in its corresponding other end position.
An embodiment of the stop which is space-saving as regards construction and favorable in terms of production is obtained by having the stop formed by at least one driving tooth arranged on the input sleeve to engage in a corresponding recess on a part of the camshaft, or vice versa. A clearance is provided between flanks of the driving tooth and contact faces of the recess. The angular clearance distance substantially corresponds to the angular adjustment of the camshaft. The adjusting bushing has a disc-shaped flange which is bolted to a corresponding counter-flange on the input end of the camshaft. The input sleeve is rotatably supported on an outer cylindrical surface of the flange and rests against a collar of the flange. The collar projects radially from the outer surface and the driving tooth engages (as an axial prolongation of the input sleeve) into an open edge of the recess provided on the collar.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.